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Guys need some help. Recently acquired a sbc 088 Vortec engine with unknown cam. It had been sitting for about a year and the carb was in need of a rebuild but ran decent. Long story short I’ve replaced everything that bolts to the long block. It ran decent for a few miles and then the plugs turned black and sooty. I’ve verified timing with a tdc tool as the balancer mark was off. Now when I blip the throttle it want to sputter back thru the carb and shoot the occasional flame. I verified timing again and then pulled the plugs and noticed how black they are. Need some advice. Specs below.

350 Vortec with 1.54 pistons (so I assume they are .045 in the hole and horrible quench unless previous owner milled the block more.

unknown cam but it’s mild as the Vortec springs appear stock.

Quickfuel 650-q carb (stock and the accelerator pump shoots good as soon as I give it throttle)
Accel HEI distributor
Summit wires
Ran TR55 plugs gapped at .045 but just purchased some 3926 to try a hotter plug.
edelbrock rpm intake
Hv oil pump (60 at idle)
6.5 psi fuel and floats are in the center of sight glass.

718900
 

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What would be a good easy tunable great outa the box carb under $500? . Aside from ls swapping it I’m hoping a carb swap would do it. Worst case changing the jets.
A Holley 4777 650 dp would work good out of the box. You can fix the QF carb but it takes some time to get it right. The jetting on a Holley 650 should be pretty close out of the box, also the FST 650 works very well also that's what I have on my 350 Vortec engine right now. Floats were set right and the idle mixture and speed settings is all I tweaked. A very good carburetor.
 

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I think you will be fine with that plug.
Just keep an eye on them like you did with the others and they will tell you if they are right or wrong.

I have ran pretty hot plugs in old school 350's with lots of compression 11+

I always hate to recommend a carb because i feel some just need help even out of the box but I really like the old AFB and AVS style carbs.
Edelbrock or Weber most run very well
 

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I wouldnt do anything with swapping parts or buying anything. Just try and tune what you have. If you can't. Find a shop that has dyno chassis. Best money spent.
 

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Just switched to an avs2 and it does much better and no fuel smell. I switched to autolite 3926 plugs. Any issues running these in Vortec heads?
Other than cracks they are great heads, best production head GM ever made for a SBC.
 

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Autolite 3926 is not for a Vortec head.
Vortec head takes .708" reach tapered seat plug....the 3926 is .750" reach gasket seat plug, typically used in aluminum heads. Not interchangeable.

Autolite 605 is the stock Vortec application plug.
 

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WOW, I wonder why that would happen. Putting the wrong plugs regardless of heat range. WOW.
 

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I threw some tr5’s in. Got some bad advise on the plugs and didn’t think to check them. ran fine with them but switched to the proper ones. Thanks for your kind words of wisdom.

Lots of good help here. Good place to learn. You cant find the stuff you need on what your doing anywhere else. Unless you find someone off the beaten path.
 
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